1. Field of the Invention
The present invention is directed to aqueous fire retardant compositions containing an emulsified or suspended colorant. In particular, the present invention is directed to aqueous fire retardant compositions containing emulsified or suspended colorants produced by the emulsion or suspension polymerization of a monomer or a mixture of monomers in the presence of at least one dye.
The present invention is also directed to processes of preparing the fire retardant compositions, containing an emulsified or suspended colorant, wherein the colorants are produced by emulsion or suspension polymerization of a mixture of at least one monomer and at least one dye.
2. Related Background Art
A variety of fire retardant solutions are known. xe2x80x9cEvaluation of Megatard 2700: A Proposed New Fire Retardant Systemxe2x80x9d, C. W. George and C. W. Johnson, U.S.D.A. Forest Service, Intermountain Forest and Range Experimental Station, General Technical Report INT-112, August 1981, describes a fire retardant system containing ammonium sulfate as the active fire retardant salt, a guar gum thickener, iron oxide as a colorant, a spoilage inhibitor, and corrosion inhibitors. In this case, the fire retardant composition is prepared by mixing the ammonium sulfate and the corrosion inhibitor to form a liquid component. The iron oxide, thickener, and spoilage inhibitor are mixed with water to form a slurry. The slurry and the liquid component are then mixed in equal volumes to form the mixed fire retardant which is then loaded onto an airplane and applied to a wildland fire. E. P. A. Artsybashev, V. G. Lorberbaum, T. G. Pirogova, and M. A. Potemin, 12 Lesnoe Khozyaistvo 43, 44 (1991) describes a fire retardant consisting of 30-37% diammonium phosphate, 16-20% urea, 8-10% ammonium chloride, 16-20% sodium carboxymethyl cellulose, 3-5% acid orange dye, and 7-20% kaolin. E. S. Artsybashev, V. G. Loberbaum, I. N. Sedina, T. G. Pirogova, and E. F. Davydov, 6 Lesnoe Khozyaistvo 40, 42 (1988) describes a fire retardant consisting of 62-75% diammonium phosphate, 23-35% urea, 2-3% sulphonol, and 0.5% acid dye applied as a 13% aqueous solution.
Phosphate solutions useful for fire-retardant compositions are described in U.S. Pat. Nos. 3,223,649, 3,257,316, 3,275,566, 3,293,189, 3,338,829, 3,342,749, 3,350,305, 3,364,149, and 3,634,234. Other fire-retardant compositions containing various ammonium salts are described in U.S. Pat. Nos. 3,309,324, 4,101,485, 4,145,296, and 4,272,414. Fire retardant compositions stabilized with galactomannan gum are described in U.S. Pat. Nos. 4,447,336, 4,447,337, and 4,606,831.
V. G. Lorberbaum, I. N. Sedina, E. E. Frolovskii, V. I. Fedorov and E. F. Davydov, 9 Lesnoe Khozyaistvo 59, 60 (1983) describes a fire retardant containing 90.2% hydrated magnesium chloride, 8.2-5.82% wetting agent, 1.25-0.89% corrosion inhibitor, and 1.25-0.89% light-resistant acid orange dye in powder form which is dissolved in water prior to application. E. A. Shchetinskii, A. M. Simskii, and E. F. Davydov, 5 Lesnoe Khozyaistvo 88 (1975) describes a fire retardant containing Rhodamine-S dye added to aqueous solutions of diammonium phosphate, ammonium sulfate, or xe2x80x9cammophosxe2x80x9d. Chemical Week, Mar. 28, 1979, at page 40, describes a fire retardant, PHOS-CHEK(copyright) XAF made by Monsanto Company (St. Louis, Mo.) which contains the active ingredient diammonium phosphate and a fugitive International Orange color that fades away after several days, as opposed to the permanent red iron oxide pigment previously used.
French Patent Publication No. FR 2172867 A describes fire extinguishing solutions that contain mono or diammonium phosphate, a solid surfactant, and a colorant. Russian Patent Publication No. RU 2022630 describes a unit for the preparation of fire extinguishing compounds. The unit contains a motor pump connected to an ejection mixer with the powder supplied from a bunker, and a static mixer in the output line.
Soviet Patent Publication No. SU 1544451 describes compositions for fighting forest fires from the air containing sodium carboxymethyl cellulose, ammonium hydrogen phosphate, ammonium chloride, urea, kaolin, and light fast acid orange as a dye. Soviet Patent Publication No. SU 15444450 describes compositions for fighting forest fires from the ground level containing urea, sulphonol, scarlet acid dye, diammonium hydrogen phosphate, and ammonium chloride. International Patent Publication No. WO 9322000 describes compositions for the prevention and the combatting of fires containing fiber/clay combinations, corrosion inhibitors, anti-cryptogamic agents, a dye, and cellulose based fibers.
U.S. Pat. No. 4,168,239 describes thixotropic emulsion concentrates, used to form fire suppressant foams for fire fighting, that contain oil, emulsifier, colorant, and an aqueous fire suppressant. U.S. Pat. No. 3,730,890 describes flame retardant concentrates formed from attapuglite clay suspended in liquid ammonium polyphosphate. U.S. Pat. No. 3,960,735 describes flame retardant polyphosphate compositions containing iron cyanide blue added to inhibit the corrosion of aluminum. The above U.S. Patents are incorporated by reference herein.
U.S. Pat. No. 3,409,550 describes fire retardant compositions containing a mixture of ammonium sulfate and diammonium phosphate in an aqueous gel. Dyes such as Rhodamine B, azo red A, naphthol orange, and pigments may be added as a marking agent. U.S. Pat. Nos. 4,839,065, 4,971,728, and 4,983,326 describe a fire retardant concentrate containing a thickening agent and a fire retardant. The diammonium phosphate, diammonium sulfate, and monoammonium phosphate blended with polyammonium phosphate are used as the fire retardant. The above U.S. Patents are incorporated by reference herein.
Colorants are chemical substances added to materials to produce color effects. The colorants used in the present invention can be aqueous dispersions of a non-fluorescent pigment or of a fluorescent pigment as described in U.S. Pat. Nos. 5,294,664 and 5,215,679. The above U.S. Patents are incorporated by reference herein.
Although the term xe2x80x9cfire retardant solutionxe2x80x9d is used herein, it is understood that such fire retardant liquid mixtures are not true solutions in which all of the components are dissolved to form a single homogenous liquid phasexe2x80x94without solid phases or other immiscible liquid phases present. It will be recognized that some of the components used may be essentially insoluble in the liquid components. That is, components such as iron oxide and titanium oxide, as well as some of the polymeric components, are insoluble in water. Nonetheless, the term xe2x80x9csolutionxe2x80x9d will be used as well as the more physicochemically correct terms such as xe2x80x9cfluidxe2x80x9d or xe2x80x9cliquidxe2x80x9d because the term is commonly used in this art. Thus, the term xe2x80x9cfire retardant solutionxe2x80x9d is used to mean the fire retardant composition formed by water and other liquid and/or solid components ready for application onto burning fuels.
The terms xe2x80x9cdispersionxe2x80x9d and xe2x80x9csuspension,xe2x80x9d as will be described below, are differentiated herein from xe2x80x9cslurryxe2x80x9d. Accordingly, phrases such as xe2x80x9cdispersion solution,xe2x80x9d xe2x80x9caqueous dispersion,xe2x80x9d xe2x80x9caqueous suspension,xe2x80x9d xe2x80x9csuspension solution,xe2x80x9d xe2x80x9csuspension,xe2x80x9d or xe2x80x9cdispersionxe2x80x9d are not interchangeable with xe2x80x9cslurry solution,xe2x80x9d or xe2x80x9cslurry.xe2x80x9d
It is conventional practice to add the components of a fire retardant solution, as a preformed concentrate, into water at a prescribed mix (dilution) ratio in order to form the fire retardant solution. There are conventionally three types of fire retardant concentratesxe2x80x94xe2x80x9cdry-powderxe2x80x9d concentrates, xe2x80x9cfluidxe2x80x9d concentrates, and xe2x80x9cliquidxe2x80x9d concentrates.
xe2x80x9cDry-powderxe2x80x9d type concentrates are simply dry mixtures of components that are mixed into water in order to form a fire retardant solution.
Mixtures of components are formed in accordance with the teachings of U.S. Pat. Nos. 4,839,065, 4,971,728 and 4,983,326 to prepare low viscosity fire retardant concentrates which are referred to as xe2x80x9cfluid concentratesxe2x80x9d. The fluid concentrate type fire retardants are delivered to the mixing or dilution location or depot in the fluid concentrates"" low viscosity concentrated form. When the fluid concentrates are subsequently diluted with water, at their prescribed mix ratios, suspended thickeners are activated and gum-thickened fire retardant solutions are prepared. The level of viscosity obtained upon dilution of the fluid concentrate can be altered by varying the amount of gum-thickener incorporated in the formulation.
A third type of wildland fire retardant concentrate, prepared according to the teachings of U.S. Pat. Nos. 3,730,890 and 3,960,735, is referred to as xe2x80x9cliquid concentratesxe2x80x9d. In this case, liquid ammonium phosphate-containing fertilizer solutions, optionally combined with color pigments, clay used as a suspension agent, corrosion inhibitors, and other functional components, form unthickened fire retardant concentrate suspensions. The liquid concentrate type fire retardants are delivered to the mixing or dilution location or depot as a high viscosity suspension. When the liquid concentrates are subsequently diluted with water, at their prescribed mix ratios, low viscosity ammonium phosphate fire retardant solutions containing, optionally, color pigment, clay and other functional components are obtained. These solutions are formed by dilution immediately prior to use in order to prevent separation and settling of the solids from the liquid.
Although both xe2x80x9cfluidxe2x80x9d and xe2x80x9cliquidxe2x80x9d type concentrates are fluid or liquid mixtures, the terms have a particular meaning in the art. The difference between the fluid concentrate and the liquid concentrate type fire retardants is apparent. A fluid concentrate exhibits a low viscosity until diluted with water. At that time, suspended thickeners are activated and the viscosity of the resultant solution remains unaffected, or increases, depending on the amount of thickener in the concentrated composition. A liquid concentrate, on the other hand, is a relatively high viscosity liquid mixture containing suspended clay, fire retardant, and colorizing pigment that, upon dilution at the prescribed mix ratio, forms an unthickened fire retardant solution.
Accordingly, the terms xe2x80x9cliquidxe2x80x9d and xe2x80x9cfluidxe2x80x9d when used in the phrases xe2x80x9cliquid concentratexe2x80x9d and xe2x80x9cfluid concentratexe2x80x9d have specific meaning. When the terms xe2x80x9cliquidxe2x80x9d and xe2x80x9cfluidxe2x80x9d are used elsewhere, they are intended to have their common meaningxe2x80x94referring to the physical phase of matter that conforms to a volume and that is substantially incompressible. Although, as described previously, the terms xe2x80x9cliquidxe2x80x9d and xe2x80x9cfluidxe2x80x9d include mixtures of liquids with undissolved solid particles.
Fire retardant solutions used to combat and control wildland fires are applied from the ground or from the air. Application from the ground is usually from a vehicle such as a fire engine, while application from the air is usually from an airplane or helicopter. It is often desirable to mark the locations that have been applied with fire retardants in order to coordinate fire-fighting activities, to conserve supplies, and to show the progress of the fire-fighting effort. Therefore, color pigments are often added to the fire-fighting product formulation at the time of the product""s manufacture.
The fuel which feeds a wildland fire varies widely from grasses to large trees. Therefore, the color pigment in the applied fire retardant must present an adequate color contrast from the background fuel to conveniently show where fire retardant has been applied. The pigmented fire retardants of the prior art, however, might contain too much or too little colorant for a particular application because, while the color and geometry of wildland fuels vary widely, the concentration of pigment is fixed at the time of fire retardant manufacture at the factory.
Accordingly, it would be desirable to have the capability of adjusting the colorant level in the fire retardant solution at the time of use relative to the amount needed to maintain visibility. This ability would both minimize the possibility of leaving unobserved discontinuities in the retardant fire break through which a fire could escape, and minimize the use of colorant in those instances when visibility is easily achieved. Either case would result in savings in cost and possibly property.
Excess application of colorant further has an impact on the aesthetics of the wildland. Towards minimizing such impact, the United States Forest Service regulates that a film of a colorized formulation must return to the color of the uncolorized film after a prescribed amount of sunlight, currently 18,000 Langleys (7.53xc3x97108 J/M2) of exposure per U.S. Department of Agriculture, Forest Service, Specification for Long Term Retardant, Forest Fire, Aircraft or Ground Application, Specification 5100-304a, February 1986. According to that specification, a 0.022 inch (0.056 cm) thick film of the fire retardant solution is applied to a glass plate. The plate is then exposed to natural light in accordance with ASTM G-24, Standard Recommended Practice for Conducting Natural Light Exposures, until 18,000 Langleys (7.53xc3x97108 J/M2) are accumulated. The requirement is that xe2x80x9cthe mixed retardant with fugitive colorant shall not be of a color different from the mixed retardant without colorantxe2x80x9d after exposure to 18,000 Langleys (7.53xc3x97108 J/M2) as provided by the above protocols.
Therefore, it is desirable for fire retardant liquids to contain colorants that are visible for a limited period of time after application but then fade and become non-visible. Colorants that fade are called fugitive colorants. The color effects that fugitive colorants impart are called fugitive colors. The pigments titanium dioxide TiO2 (not presently used commercially in wildland fire retardants) and iron oxide Fe2O3 do not produce color effects that inherently fade. Thus, to the extent that titanium dioxide is opaquely white and iron oxide is strongly red, they are non-fugitive colorants. Consequently, as non-fugitive colorants, titanium dioxide and iron oxide are not suitable for use in a truly fugitive colored fire retardant solution.
The fire retardant systems of the present invention includes an ante-colorized fire retardant composition and an aqueous pigment dispersion colorant that, in combination, form a colorized fire retardant composition. The colorant system of this invention includes the aqueous pigment dispersion colorant and the dispersion""s pigment formed from a polymer and a dye. The pigment has properties effective to allow the pigment to be dispersed in water to form the aqueous pigment dispersion and to cause the aqueous pigment dispersion to remain stable, resisting sedimentation without agitation, until the dispersion is used to form colorized fire retardant liquids.
The aqueous pigment dispersion colorant is added to the ante-colorized fire retardant composition, in order to form a colorized fire retardant composition, at any time prior to or during discharge of the thus formed colorized fire retardant composition. The colorized fire retardant composition is generally discharged towards the fuel, or potential fuel, of a fire that the fire retardant composition is used to try to control. Accordingly, xe2x80x9cfuelxe2x80x9d is that which can burn. Fuels include, for example, grass, brush, shrub, trees, timber, artificial structures and constructions, and mobile units.
As used herein, the phrase xe2x80x9cante-colorized fire retardant compositionxe2x80x9d is used to indicate the fire retardant composition or liquid to which is added the colorant employed by the present invention. The ante-colorized fire retardant composition or liquid can itself be already colorized. Further, the ante-colorized fire retardant composition or liquid can be a solution, a mixture, an emulsion, or a suspension.
The term xe2x80x9cdyexe2x80x9d as used herein means colorant compounds that are dissolved in the media in which they are used. The term xe2x80x9cpigmentxe2x80x9d as used herein refers to colorizing compounds that are insoluble in the media in which they are used and consequently are present as solid particles.
The terms xe2x80x9cemulsion,xe2x80x9d xe2x80x9cdispersion,xe2x80x9d and xe2x80x9csuspensionxe2x80x9d as used herein mean solid/liquid mixtures in which the solid does not readily separate out from the liquid, prior to the use of the emulsion, dispersion, or suspension, even in the absence of agitation or some other energy being imparted to the dispersion. The liquid can include dissolved solids. The term xe2x80x9cslurryxe2x80x9d as used herein means a solid/liquid mixture in which the solid does separate out from the liquid in the absence of agitation or some other energy being imparted to the mixture. It is understood by one of ordinary skill in the art that, other parameters being equal, slurries are formed by larger sized particles than the smaller sized particles that form emulsions, dispersions, or suspensions.
The important advantageous property of the aqueous pigment dispersions of this invention is the resistance of the aqueous pigment dispersions to settling of the solid components from the liquid components. Accordingly, it is understood that as used herein, the terms emulsion, dispersion, and suspension can be used interchangeably except where a specific process is recited that would not produce an emulsion, a dispersion, or a suspension. The use of one term, for example xe2x80x9cdispersion,xe2x80x9d below generally includes the other terms such as emulsion or suspension. The solid/liquid mixtures of the colorants of this invention will be generally referred to below as xe2x80x9caqueous pigment dispersionsxe2x80x9d while the pigment in the aqueous pigment dispersion will be generally referred to below as xe2x80x9caqueous dispersion pigment.xe2x80x9d
The percentage units used herein to describe composition constituents are in percent by weight unless specifically indicated otherwise.
In one aspect, this invention utilizes a pigment containing a dye in an amount effective to impart a desired level of color intensity to the pigment. The pigment comprises a water insoluble polymer formed from at least four monomers, at least one monomer selected from each of the following groups (a) through (d):
a. from about 40% to about 78.5% total polymer weight of a water insoluble vinyl monomer free of polar groups;
b. from about 15% to about 35% by total polymer weight of vinyl nitrile;
c. from about 1.5% to about 5% by total polymer weight of a vinyl monomer containing a least one sulfonate group; and
d. from about 5% to about 20% total polymer weight of a polar vinyl monomer selected from:
(i) polar acrylate esters;
(ii) polar methacrylate esters;
(iii) vinyl acetate;
(iv) a substituted acrylamide containing hydroxyl or carboxylic ester groups; or
(v) mixtures thereof.
The aqueous pigment dispersion includes water in an amount to provide a total solids content of from about 0.5% to less than 100% by weight.
In another aspect, the present invention utilizes a colorant, which is an aqueous emulsion of a water insoluble tetra polymer which contains a fluorescent or non-fluorescent dye, comprising:
a. a water insoluble tetra polymer from about 25-50% by weight;
b. a dye from about 0.1-10% by weight;
c. an anionic emulsifier from about 0.2-10% by weight; and
d. water from about 30-74.7% by weight; with the water insoluble tetra polymer comprising:
A) a water insoluble vinyl monomer free of polar groups from about 52-65% by weight;
B) acrylonitrile from about 25-35% by weight;
C) a vinyl monomer containing at least one sulfonate group from about 1.5-4.%% by weight; and
D) a polar vinyl monomer from about 5-15% by weight selected from:
i) polar, nonchlorinated, nonepoxidized acrylate esters;
ii) vinyl acetate; or
iii) a substituted acrylamide containing hydroxyl or carboxylic ester groups.
In yet another aspect of the present invention, a colorized fire retardant liquid utilizes a colorant, which is an aqueous emulsion of a water insoluble tetra polymer which contains a fluorescent or non-fluorescent dye, comprising:
a) a water insoluble tetra polymer from about 35-45% by weight;
b) a dye from about 0.5-7% by weight;
c) an anionic emulsifier from about 0.5-5.5% by weight; and
d) water from about 46-64% by weight;
with the water insoluble tetra polymer comprising:
A) a water insoluble vinyl monomer free of polar groups from about 52-65% by weight;
B) acrylonitrile from about 25-35% by weight;
C) a vinyl monomer containing sulfonate groups from about 1.5-4.5% by weight; and
D) a polar vinyl monomer from about 5-15% by weight selected from:
i) polar, nonchlorinated, nonepoxidized acrylate esters;
ii) vinyl acetate; or
iii) a substituted acrylamide containing OH or carboxylic ester groups.
In still another aspect, the present invention utilizes a colorant which is a fluorescent or non-fluorescent pigment comprising:
I. a tetra polymer, which is comprised of:
a) a water insoluble vinyl monomer free of polar groups from about 52-65% by weight;
b) acrylonitrile from about 25-35% by weight;
c) a vinyl monomer containing sulfonate groups from about 1.5-4.5% by weight; and
d) a polar vinyl monomer from about 5-15% by weight selected from:
1) polar, nonchlorinated, nonepoxidized acrylate esters;
2) vinyl acetate; or
3) a substituted acrylamide containing hydroxyl or carboxylic ester groups; and
II. a fluorescent or non-fluorescent dye.
Aqueous pigment dispersion colorants, being already dispersed, are more easily dispersed in a fire retardant solution than are dry-powder pigment colorants. Without being bound by theory, this difference in the ease of dispersion is believed to result from the fact that the pigment particles are present in the aqueous pigment dispersions as individual, discrete and separate particles whereas the dry-powder pigments tend to exist in the dry state as agglomerates. Such agglomerates require a considerable energy input to achieve the same degree of ultimate dispersion as the pre-dispersed pigments in the aqueous pigment dispersions.
Accordingly, the colorant component of the present invention, which are aqueously emulsified or suspended pigments, can be advantageously added directly to a neat fire retardant solution, in order to form the colorized fire retardant solution of the present invention, at any time before applying the colorized fire retardant solution to a fire or to fuel threatened by a fire. It is particularly advantageous to add the aqueously emulsified or suspended colorant shortly before the thus formed colorized fire retardant solution is used, such as at the time that the delivery (or application) vehicle is being loaded with the fire retardant solution, or just before, or as the colorized fire retardant is discharged to the fuel. The emulsified or suspended colorant is of a particle size effective to maintain the dispersion of the pigment particles, with little or no agitation, prior to use of the dispersion. By contrast, agitation is required when pigment slurries are used, without which the solid particles would settle out from the liquid prior to using the slurry.
The colorized fire retardant solutions of the present invention are sufficiently stable from settling or separation of the dispersed pigment from the liquid so that the colorized fire retardant solutions can be mixed ahead of the time of use. In particular, the viscosity stability during storage may be improved when the aqueous pigment dispersion is present. Nevertheless, it is advantageous to mix the fire retardant solution at or shortly before use in order to be able to adapt to changing visibility, fire, and fuel conditions.
Generally, fire retardant solutions are applied to large fires from the air by means of being released from helicopters or fixed-wing aircraft. Some aircraft can drop partial loads by discharging from different compartments or by shutting off the discharge after partial release. Nevertheless, in order to maximize the payload of fire retardant solution, other cargo is minimized. Consequently, it is preferred that the mixing to form the colorized fire retardant solutions of this invention be performed just prior to or during the loading of the thus formed colorized fire retardant solution onto the aircraft.
In certain situations such as, for example, when the fire retardant solution is applied from a hose or applied in multiple metered doses, it is advantageous to add the aqueously emulsified or suspended colorant just before or as the colorized fire retardant is discharged to the fuel.
By a method of the present invention, the aqueously emulsified or suspended colorant component can be added to the fire retardant solution to form the colorized fire retardant solution as the colorized fire retardant solution is being discharged to the fuel. This method advantageously allows immediate and continuing adjustment of the color component of the colorized fire retardant solution in response to changing visibility, fire, and fuel conditions.
The present invention utilizes pigment powders that are polymeric compounds incorporating at least one dye constituent. It is preferred that the dye constituents are incorporated into the polymeric compound during the polymerization of the constituent monomers that form the polymeric compound. The polymeric compound can be formed from one or more monomer compounds of any convenient moiety or moieties. The aqueous pigment dispersion colorant of this invention is formed by dispersing the polymeric pigment powder (incorporating the dye) in water or other aqueous media effective to form an emulsion or suspension. One particular process by which the polymeric pigment powder (incorporating the dye) is dispersed in water or other aqueous media is by polymerization in situ within the aqueous medium in which the polymeric pigment powder thus formed is dispersed.
According to one embodiment of the present invention, a colorized fire retardant solution is formed from a fire retardant solution and a colorant in an amount effective to colorize the fire retardant solution, wherein the colorant is an aqueous dispersion of a fluorescent or non-fluorescent pigment, and wherein the aqueous dispersion is an emulsion or a suspension.
Another embodiment of the present invention is directed to a method for forming a colorized fire retardant solution from an ante-colorized fire retardant solution. The method comprises adding an aqueous dispersion of a fluorescent or non-fluorescent pigment to the ante-colorized fire retardant solution, in an amount effective to colorize said ante-colorized fire retardant solution, at a time proximate to discharging the colorized fire retardant solution to a fuel. The method can include monitoring a parameter and adjusting the amount of aqueous pigment dispersion in response to the monitored parameter. The amount of aqueous pigment dispersion can be added incrementally, at a rate effective to colorize the ante-colorized fire retardant solution, as the colorized fire retardant solution is loaded onto the applying vehicle or, possibly, as it is discharged from the applying vehicle onto the target fuel. The rate can be adjusted in response to the monitored parameter.
Yet another embodiment of the present invention is directed to a method to optically mark fuel comprising adding a colorant to an ante-colorized fire retardant solution, at a rate effective to colorize the ante-colorized fire retardant solution; discharging the colorized fire retardant solution to form a discharge; directing the discharge to mark the fuel; monitoring a parameter; and adjusting the rate that the pigment is added responsively to the monitored parameter.
The parameter monitored can be any conveniently measured property such as a color of the fuel, a reflectance of the fuel, a color of the colorized fire retardant solution, the wind conditions, the ambient temperature, or the temperature or smoking character of the fire.
The present invention, as described above, utilizes pigment particles that are polymeric compounds incorporating at least a dye. The aqueous pigment dispersion colorant of this invention is formed by dispersing the polymeric pigment particles (incorporating the dye) in water effective to form an emulsion or suspension. The average particle size of the polymeric pigment particles used to form the aqueous pigment dispersion colorant of this invention should be less than 10 xcexcm, preferably less than about 5 xcexcm, more preferably less than about 1 xcexcm average particle size. The smaller size particles are more effective at remaining dispersed or suspended in water, without settling, when agitation or other energy is not imparted to the emulsion, dispersion, or suspension.
It is advantageous for the average particle size be from about 0.35 xcexcm to about 0.55 xcexcm. It is more advantageous for the average particle size be from about 0.35 xcexcm to about 0.45 xcexcm. The more consistent small size distribution causes the emulsion, dispersion, or suspension to be better emulsified, dispersed, or suspended in the water.
The pigments used in the aqueous pigment dispersion colorant of this invention can be processed by any convenient method to produce particles with sufficiently small particle sizes that will remain in an emulsion, dispersion, or suspension. For example, theoretically solid pigments can be ground to small particle sizes. However, it is only with great difficulty that grinding processes can produce average particle sizes less than about 1 xcexcm. Accordingly, it is preferred that the polymer pigments of this invention be formed by an emulsion or suspension polymerization process. Such processes can easily form particles in situ having average particle sizes less than 1 xcexcm, and as low as about 0.01 xcexcm or less.
It may be desirable to include opacifying pigments such as, for example, titanium dioxide, by incorporating such pigments in the aqueous dispersion pigment. Such components can be incorporated by any convenient method such as, for example, by inclusion during the in situ polymerization of the fugitive pigments to form the aqueous pigment dispersions of this invention. Such components may also be conveniently included in the ante-colorized retardant solution.
It is important that the pigments of this invention remain dispersed as an emulsion, dispersion, or suspension. Accordingly, constituents that cause agglomeration should not be included, unless the agglomerating effects are effectively counteracted, in the flame retardant compositions used in this invention. For example, the presence of attapulgus clay in some fire retardant solutions leads to the agglomeration of some pigment dispersions. It is understood that it is the agglomeration that should be avoided rather than any particular ingredient. Thus, any potential agglomerating ingredient should be counteracted by any convenient effective dispersing ingredient such as, for example, a dispersing agent or a surfactant.
The fire retardant systems of the present invention can include conventional pigments supplemented by an aqueous emulsified or suspended copolymer/dye component (aqueous pigment dispersion colorant). When used as a supplemental colorant, the amount of the aqueous pigment dispersion colorant can be any convenient amount effective to provide the desired properties. In one example, about 0.35% by volume of the pigment dispersion improved the coloration of the ante-colorized fire retardant solution to an acceptable level.
The fire retardant system of the present invention can include any convenient opacifier such as, for example, titanium dioxide, potassium titanate, zinc oxide, zinc sulfide, lead salts, antimony oxide, earth-tone colored iron oxides, iron phosphates and the like, and selected extender or filler pigments such as non-reactive clays, calcium sulfate and mixtures thereof at a level effective to provide a desired amount of opacity. The opacifier can be any hiding pigment or any filler powder that (i) is insoluble and non-reactive in the fire retardant solution and (ii) becomes acceptably inconspicuous after the application of the fire retardant solution. It is preferred that the opacifier is able to opacify or hide the substrate without causing significant abnormal colors relative to the applied environment. Thus, for applications to forest fires, an earth tone would be desirable as a background color to which the colorized liquid fades. Such earth tones can be formed by using brown iron oxide with a white pigment to lighten the brown color as desired to blend with the background color of the area of dispersal as the fugitive color fades.
The color properties of the fire retardant system of the present invention increase with applied film thickness. The opacity (hiding power), the transmitted color intensity of the wet film, and the reflected color intensity of the dry film increase with coverage level. The fire retardant system of the present invention provides effective visibility at the coverage levels typically required in the field. For example, fire retardant coverage levels of the present invention equal to and above about 4 gpc (gallons per hundred square feet), (0.0014 M3/M2 (M3 fire retardant per M2 area sprayed) or 1.4 L/M2 (liters per square meter)), equivalent to an applied film greater than 0.064 inch (0.163 cm) thick, result in opaque films with the hiding equivalent of 1.0% iron oxide but with a considerably greater intensity of red. Such increased color is significant for use in fire situations such as, for example, in tall fuels where the fire retardant solution penetrates and covers the fuel complex from the tree crowns to the ground. This results in significantly less solution being visible on top of the tall fuel. In such situations, coverage levels above 4 gpc (1.4 L/M2) are typically needed to control the fire. Hence, the color is correspondingly increased, thereby providing adequate visibility.
The aqueous pigment dispersion colorant utilized in the present invention can be a pigment comprising any convenient polymer, copolymer, terpolymer, or multipolymeric blends incorporating any convenient non-fluorescent or fluorescent dye. For example, an aqueous dispersion of non-fluorescent or fluorescent pigments similar to those described in U.S. Pat. Nos. 5,294,664 and 5,215,679, can be used.
The aqueous pigment dispersion colorant employed by the present invention is an emulsion or suspension of a pigment having any convenient particle size effective to provide the necessary emulsion or suspension properties and the necessary coloration properties. In general, smaller size and higher surface area are desirable. In one embodiment, the pigments have average particle diameters of less than about 10 micrometers. In another embodiment, the pigments have average particle diameters of less than about 5 micrometers. In yet another embodiment, the pigments have average particle diameters of less than about 1 millimeters. For example, when the pigments described in U.S. Pat. Nos. 5,294,664 and 5,215,679 are used, it is preferred that the pigment has an average particle size from about 0.01 xcexcm. The aqueous dispersion can include anionic surfactants, opacifiers, extenders, dispersant and/or other functional components to enhance performance.
An example of this invention utilizes a pigment that is a polymer formed from at least four monomers: a water insoluble non-polar vinyl monomer which is advantageously styrene; a vinyl monomer containing sulfonate groups which is advantageously sodium 2-acrylamido-2-methylpropane-sulfonate; a polar vinyl monomer which is advantageously hydroxypropyl methacrylate, vinyl acetate, a polar, nonchlorinated, nonepoxidized acrylate ester, or a substituted acrylamide containing hydroxyl or carboxylic ester groups; and a vinyl nitrile which is advantageously acrylonitrile.
The fluorescent pigment that can be used in this invention includes any convenient powder incorporating any convenient fluorescent dye such as, for example, benzothioxanthene, xanthene, coumarin, naphthalimide, benzoxanthene, perylene, and acridine. The dye can be water soluble or insoluble, anionically or cationically charged, or nonionic.
The non-fluorescent pigment that can be used in this invention includes any convenient powder, effective to form an aqueous dispersion, incorporating any convenient non-fluorescent dye such as, for example, those dyes described in the Pigment Handbook, edited by T. Patton, Vol.1, Wiley-Interscience. The dye can be water soluble or insoluble, anionically or cationically charged, or nonionic.
The ante-colorized fire retardant solution to which the aqueous pigment dispersion colorant of this invention is added can be formed by any convenient method such as (i) by mixing a dry powder fire retardant formulation with water, or (ii) by mixing a fire retardant fluid or liquid concentrate with water. As described above, the aqueous pigment dispersion colorant of this invention must not agglomerate when added to the ante-colorized fire retardant solution. Accordingly, the ante-colorized fire retardant solution should not have any agglomerating component such as, for example, attapulgus clay unless the agglomerating component""s action is effectively counteracted.
Tests on the fire retardant solutions of the present invention showed that their viscosity stability, corrosivity, and pumpability would not present any problems to use. Further, tests on the freeze-thaw characteristics of the aqueous dispersion pigment showed that their freeze-thaw stability would not present any problems to use.